The Population of the United States Compared with the Population of the Principal Countries of Europe from 1800 to 1900, Inclusive

Written words requiring one hour to read could not convey as much information as this chart gives. In considering the slope of the curve for the United States it must be remembered that the slope of a curve does not indicate the percentage rate of increase or decrease. The increasing slope of the United States curve does not in itself prove any increase in the percentage rate of growth. Compare Fig. 121

COMPARISON OF CURVES

The reader should keep constantly in mind when viewing Fig. 120 that the slope of a curve line crossing a field ruled with ordinary rectangular co-ordinate lines on an arithmetical scale tells nothing about the percentage rate of growth from period to period. The slope of the United States curve is very much steeper in the upper portion of Fig. 120 than in the lower portion, but the greater slope does not prove that we are growing more rapidly on a percentage basis than early in the century. The slope of a curve plotted on a natural scale of rectangular co-ordinates shows only the size of the increments added from period to period and it tells nothing whatever about percentage growth.

Fig. 121 has been drawn to assist in proving the preceding statement regarding curve slope. Starting with one dollar, it was assumed that a uniform increase of 10 per cent of the accumulated amount would be made at the end of each year. This is the same as though the dollar were placed at 10 per cent compound interest. At the end of thirty-six years it can be seen that the one dollar has increased to nearly